Astronomers announced today that the star 55 Cancri — known to have had a system of planets for some time — is now known to have at least five planets orbiting it. The existence of a fifth planet was just confirmed.

This is extremely cool for several reasons. For one, 55 Cancri is a sunlike star– it has roughly the same mass and age as the Sun. This means that systems like this might be common for stars like the Sun. Moreover, 55 Cancri is pretty close by: 41 light years, a short walk as far as the Milky Way is concerned (the MW is 100,000 light years across). Finding a system so close implies that they are common throughout the galaxy.

Second, this newly-discovered fifth planet orbits 55 Cancri in 260 days at a distance of 116 million kilometers, putting it smack dab in the "habitable zone" of the star. In other words, a normal run-of-the-mill planet at that distance will have a temperature range likely to include that of liquid water. This does not mean it has water, or life, or is earthlike in any way! It just means that it’s in the right spot, which is an important, but not sufficient, condition for water.

Most likely this is another gas giant planet; its mass is 45 times that of Earth. This is half the mass of Saturn and twice that of Neptune, so that makes it a giant. So it won’t have life as we know it, most likely. However, gas giants tend to have big moons, and in our solar system they can be as big as Mercury! It’s not too much of a stretch to imagine a large moon around this planet orbiting 55 Cancri that might look a lot more like Earth. There’s now way to know now– our tech is nowhere near good enough to detect any moons around the planet, let alone get an image of them. Someday…

I’ll add that that some news articles online will breathlessly call this an earthlike planet; it’s not. Let’s be clear about that right away. It’s a giant, probably more like Neptune.

Still, this is extremely cool. No other star is known to have this many planets. Most planets that have been discovered, in fact, have giant Jupiter-like (or bigger) planets orbiting close in to the star, and models of how they form indicate it’s unlikely those systems would have lots of other planets; the big planet would have tossed them out of the system. So seeing a system with five planets (and they all have roughly circular orbits, too, indicating a lot of stability in the system) indicates that our own solar system is not unique. There is at least one more out there… and all the indicators point toward there being more systems like this out there. A lot more.

Incredible. In 1995 we didn’t know if there were planets at all orbiting sunlike stars, and here we are, barely a decade later, finding entire solar system analogs around nearby stars. This news is so exciting!

The next step is to find more like this, of course, and to keep banging away on this and other stars to find lower and lower mass planets. The goal is to find a planet that has roughly Earth’s mass (I’ll be happy with twice our mass) in the habitable zone of a nearby star. When that happens… well, won’t that be a day?

I’ll note that it took 18 years of observations to nail down this planet, because it was so hard to detect. The labor that went into this is phenomenal. We keep looking, and we keep learning more, and we keep finding cooler stuff the more we look. That’s what this is all about.

Note: Sorry if email and feed readers got this sent to them more then once. An ad was overlapping the image, and I had to edit the entry.

OK, so this whole post is just way too cool, and then you go and drop in your last two sentences, which are downright poetical: Well done.

Once again, of course, it all comes down to funding to improve technology, to develop space-based telescopes like Hubble only moreso, to research new propulsion systems and more exotic and useful robotics. And who holds those purse-strings? Guys who are still not entirely convinced that Galileo was right, who think Darwin is the antichrist, and who redact perfectly reasonable reports on climate change by their own scientists. The best they’ll fund is some smoke-and-mirrors Apollo Redux and Neil Armstrong Goes To Mars, both of which have commercial mineral access at their core and neither of which threaten their simple view of a tidy little empty universe.

Hubble is wonderful, but with the advent of Adaptive Optics we can now get higher resolution images from ground-based telescopes, and of course it’s much cheaper than putting things like Hubble in orbit. Long term, our goals should be to put some AO scopes in orbit, but for the mean time, building a lot on Earth will have a more immediate payoff for lower cost.

That’s great news! Unfortunately it’s going to take another decade or so until we can see if there are moons and another painstaking long time until we can tell what kind of moons they are. Even then, if we find that there is an earth-like, habitable moon, we won’t be able to go there to explore, live and maybe find life for many generations if ever.

Cello: You don’t need Adaptive Optics systems in space, they are used to compensate for the blurring of Earth’s atmosphere.

I suspect what you meant is that we need interferometers in spaces, pairs or clusters of small telescopes spread over large distances combining to create a very long baseline and a magnitude of improvement in resolving power.

There is even talk that we need to get telescopes out beyond the inner solar system and all the dust it contains — but I think we’d probably settle for bigger scopes nearby for now.

This discovery is certainly one in the eye for the ridiculous Privileged Planet hypothesis (that Earth is so uniquely “designed” to support intelligent life, that there had to be a creator involved). Sure, the supporters will belittle the discovery, but this is just one of the first cuts that real science is going to deliver over the next few decades.

I have every confidence that it will be shown within a few decades that Earth is but one planet amongst billions, millions of which are Earth-like. No doubt, by then, the creationists will have a new story to spin, but it won’t do them any good. Science will never be their ally.

Um tacitus? I’m a creationist, and I have never once said that this is the only planet with intellegent sapient life on it. Maybe I’m more open minded than other creationists, but I’ve always felt that there are countless planets with life much like our own. Why do I say our own? Because if it is a God that created the universe and plunked people down on all of the earth-like planets out there, then they’d (the intellegent sapient life) roughly be the same as ours. I understand that evolution would state otherwise, but until we can actually see intelligent sapient life in other star systems, we’re allowed to have our own opinion… aren’t we? No? Oh.

In fact, I knew that there were planets rotating around other stars long before they were discovered… the discovery of new planets just strengthened my faith, not wrecked it.

Well… let’s have it. Cut me to pieces because I stated my opinion.

By the way, I just want to say: Nice planet. I hope they find more… which they will. I too am reminded of Contact, when asked how many other systems are there and David Morse pours sand out of his hand. I’d wager it’s closer to the amount of sand on the beach than just his hand… if not more. (Sorry… I had to quote the movie… haven’t read the novel)

You are definitely in the minority of creationists when it comes to belief in life on other planets. Most creationists that I have met and read would regard the existence of life, and especially intelligent life, on other planets as impossible given the most common literal reading of the Bible.

I think you will find that most creationists would assert that your position that there are multiple Earths out there with other human beings goes against what the Bible teaches about Man’s special place in the Universe and his special relationship with God. It certainly makes the story of Adam and Eve, and the teaching of original sin a little more tricky, unless you assume exactly the same thing has happened on every planet.

But, on the other hand, if one day we do discover intelligent life on another planet, I do not doubt for one second that most creationists will simply find a way to accommodate this new finding into their belief system. It will be as it ever was, given the advance of scientific discovery since creationism was last a reasonable position to take, back in the Middle Ages. Since then we have discovered that the Earth is billions of years old, is not the center of the Universe, is not even the center of our galaxy or solar system, and yet creationist thought has adapted and survived through all that. I have even had creationists tell me that if an alien visitor dropped off recordings of our own history which showed that we did evolve and were not just dumped here 6,000 years, they would still remain a staunch creationist (“the aliens must be lying to us”).

By the way, you didn’t *know* that there were other planets around other stars before the first one was discovered. You knew that it was likely, even highly likely. There is a big difference — as big as the one between religious revelation and scientific discovery.

@Darth Curt:
There is some truth in your words. I do believe in god, too, but I’m no creationist. But I’m with you: There is no reason that the existence of god requires a unique earth with unique inhabitants.

force users? Well, when Phil mentiond the moon, I was just thinking of the Endor moon of Star Wars 😉

And: Let’s see what we will find next – there is much too find, and too find out!

Curt: S’okay, and it wasn’t even particularly directed at you (after all, the first response on this post went right into tweaking noses). I just like civil discussions, not jihads over dogma. Tacitus is pretty good when it comes to civility.

Not to split hairs… well, yes, to split hairs…

>> Most creationists that I have met and read would regard the existence of life, and especially intelligent life, on other planets as impossible given the most common literal reading of the Bible.

This confliates “creationist” with “fundamentalist.” Almost all fundamentalists are creationists, but not all creationists are fundamentalists. It just so happens that the most obnoxious creationists also tend to be fundamentalists as well. There are analogs in our (the pro-evolution) camp which need not be elaborated on for they are obvious by inspection.

Thought experiments concerning elder races that circumvent Fermi’s Paradox aside, extraterrestrial life doesn’t really affect the ideological validity of creationism (to creationists, mind). Genesis deals mostly with the Earth, and only mentions the sky in passing. Since anything in the sky, including space aliens, can be put into that particular ‘day’ in the creation timeline, then it stands to reason that they were created then and their sudden presence would not surprise. Additionally, given the inherent presumption of the Primacy of Man and the Importance of Earth, elder races could be discounted through the use of Last Thursdayism (I’m sorry for the thought-terminating cliche, creationists, but I don’t know what else to call it). ‘Sides, the rest of the universe only took a day or two; Earth took a whole six. Take that, aliens.

Of course, this is assuming a creationist content in their beliefs without assuming it to have scientific support (as it does rely on Last Thursdayism)… a category in which most of the ‘obnoxious’ creationists sadly do not apply.

@tacitus… Knew… Believed… semantics. But you’re right. I believed that there was more than this planet. I have some pretty open-minded ideas about the other planets’ Adam & Eve’s too… it would probably make me very unpopular in a “traditional Creationist” study group. As we are on topic and there’s no “sword rattling”, the way I see it, with the Universe as old as it is, why wouldn’t make sense for God (if you are a theist) to have other projects going on? The 4.5 Billion years that our Earth took to be created (my opinion) is long enough to have other things going on. He is God after all… he can multi-task.

Pick up Allen Steele’s science fiction novel “Coyote” the next time you’re in a book store. It tells the story of a group of revolutionaries who kidnap a starship and travel to, of all places, 55 Cancri where they civilize a large moon orbiting (again, of all things) a gas giant planet in the star’s habitable zone!!

How is proximity an indicator of frequency? I would think sample size and results would be the only real measurement. The fact that the system is close merely indicates the ease with which we can detect planets as opposed to systems that are more distant and, as such, present more of a measurement problem.

Why must people use scientific discoveries as a vehicle to promote their own anti-faith or faith-based agendas? The very fact that we still have SO many questions proves that anyone who attacks another person’s answers is ignorant and close-minded. I personally beleive in Creation, and I beleive that it and evolution are not mutually exclusive. But am I right? How should I know? Maybe they are. Maybe we are a Priveleged Planet, maybe there are gazillions of carbon-copies of Earth…why not just KEEP LEARNING as a society about what’s “out there”, present the answers we do obtain, and leave the personal conclusions of faith to the individual? Human scientific knowledge would not be so divisive if we didn’t try to draw conclusions for each other from the little factoids we are fortunate enough to obtain.

If we can accept that we don’t know everything, then we can rule out nothing. To call anyone obnoxious because of a deeply held belief is, in fact, obnoxious.

Let’s say you have a blind man sitting in a chair bolted to the floor in a sub-sub-sub basement (maybe it’s a parking garage, it’s huge). His legs are tied to the chair, and elsewhere in the basement there are a random number of dummies in chairs, randomly placed. At the feet of the blind man, within reach (though he has to stretch) are lengths of PVC pipe that can be screwed together to make a pole of increasing length.

The blind man can only detect the dummies first by waving his arms, then by waving a pole. Now for a basement of finite volume, with a random number of dummies being placed randomly, it can be assumed that the average dummy density of the basement is constant (as no other data is known to refine the resolution of the assumption). Therefore, should the blind man be able to touch a dummy with his hands, he could reasonably establish as a working hypothesis, knowing only that there are a random number of dummies randomly placed, that dummies must be common for one to just happen to be right next to him. How the blind man tests this theory is by building a pole and seeing how many other dummies he can thwack with poles of varying lengths, remembering their positions and then getting that sample size you’re looking for.

It’s not a leap of statistics, it’s the statistics of developing a working hypothesis based on a small sample size and is used as the basis of most polling nowadays (where 100 to 500 people are supposed to be representative of millions).

>> To call anyone obnoxious because of a deeply held belief is, in fact, obnoxious.

I was afraid of that.

There are three seperate sets of people [limited to my previous post]: creationists, fundamentalists, and obnoxious people. Someone can be, in a non-exhaustive list, a creationist, a fundamentalist creationist, or an obnoxious [whatever]. Just because one is in one set does not make them obnoxious. It is just that when there are obnoxious people who are creationists as well, the most obnoxious of those tend to be fundamentalists as well.

Mr Ambler…I think what he meant was: if after a century of looking, we finally found a large system like this, then we could reasonably expect to go another century before finding another, assuming the rate of discovery remains constant. Hence, they must then be rather scarce. So since we found one after only a decade, perhaps only another decade is needed before we find the next…and the next…and the next, which implies that they are fairly common. Intellegesne?

I’m sorry if I needlessly injected creationism vs evolution into the mix. I must admit that it is an interest of mine — the political debate, that is.

The Privileged Planet hypothesis is a recently opened front by creationists as another justification for getting their beliefs accepted as science in the public education system. It has many parallels with the anti-evolution position, using a mix of dubious (and unverifiable) statistics and incredulity to fight what they seen as the unreasonable amount of materialistic thinking in astronomy, cosmology, and related fields.

In many ways, it is to physics as Intelligent Design is to biology and evolution. And in the same way that ID has sought to bring a veil of scientific respectability to creationist thought, the PP hypothesis attempts to do the same in astronomy, supplanting out-dated arguments such as a widely varying speed of light to explain why we can see light from stars billions of light years away in a universe only 6,000 years old.

The beauty of the PP hypothesis, from the creationist standpoint, is that it is essentially unfalsifiable. It may be 100s of years before we have a good handle on how much life is out there if any (at least, in our galactic neighborhood), and even if we find some, how much life, and how varied does it have to be to claim that our Universe was not “designed for life”?

No doubt, the more we discover, the more specific claims made by PPH adherents will fall by the wayside (just like ID), but they will simply adjust and move on to other claims. If the galaxy is devoid of life, it will prove to them that Earth was designed specially with us in mind, but it the galaxy is teeming with life, they will claim that it shows that the designer created the Universe to be friendly to the abundance of life.

Andy, yeah, I was thinking that the probability of a really chunky moon is not large, but given that we have both Triton and our own moon here (both believed essentially to be captured through collisions), it ain’t zero either.

I understand these close-in giants are supposed to have got there by migrating from beyond the frost line: I wonder what effect that process might have on any satellites. 55 Cnc e could have had a decent sized moon once, yet it might have boiled away by now. Imagine what Triton would do if it were put in orbit round Venus.

– an area in the direction of the constellation of the Unicorn (Monoceros) during 60 days,
– followed by a short (26days) and a very long (150 days) pointing in the opposite direction, in the constellation of the Snakes tail (Serpens Cauda).

CoRoT obtains “light curves”, i.e. it measures the light coming from a very large number of stars with unprecedented precision for a hitherto unheard length of time. During each set of observations more than 12000 light curves have been obtained, with almost uninterrupted data.

It is now clear that CoRoT will instigate a breakthrough in both of the fields of science that it applies to.

The scientific impact of CoRoT relies on its three major characteristics never reached before for which the satellite fulfils and surpass its originals specifications:

– the precision with which the satellite is working, which is set by physical laws â€“ not by the working of the instrument (the data are thus photon noise limited essentially over all magnitude ranges);
– the duration of the observations on the same star;
– the continuity of these observations, which have almost no interruption over these very long periods.

And CoRoT finds that essentially every star it observes varies.

– CoRoT is discovering exo-planets at a rate only set by the available resources to follow up the detections,
– CoRoT has detected solar type oscillations in solar type stars at a level so far unprecedented apart for observations of our own Sun,
– CoRoT is observing all kinds of activity on a large domain of frequencies from multi-mode oscillations, signature of erratic superficial motions, to the signature of differential rotation â€“ as seen by the different periods of the passage of sunspots at different latitudes.

>> – CoRoT is discovering exo-planets at a rate only set by the available resources to follow up the detections,

D’ya think they have an @Home-type system we can sign up for? I’d be willing to give my extra runtime cycles to this rather than protein folding (Rosetta’s gotten a LOT out of TMA-1)…

>> Yeah, what Centipede said. Just shorter.

And lacking dummies. For dummies are an important metaphor. Or something.

>> Privileged Planet

Just seems like a rehash of the anthropic principle to me. The only novel thing about it is that it comes out and tries to describe, in ‘scientific’ terms, the Primacy of Man traditionally assumed in Abrahamic religion… unless I’m missing something, which is quite possible.

The fifth planet of 55 Cancri is predicted to be about half the mass of Saturn. Saturn’s Titan has such strikingly similar conditions to Earth except for its cold surface temperature. Like Earth, Titan has a mostly nitrogen atmosphere. Titan also has a similar atmospheric pressure and it is fairly large at slightly less than half the radius of Earth. It is also substantially more massive than Earth’s Moon. Even assuming the hypothesis of the gas giant article is correct, I don’t see how the habitability of moons around the fifth planet in 55 Cancri can ipso facto be ruled out when you the take the life-bearing characteristics of Titan and push them “in the ballpark” of habitability by 55 Cancri f’s orbit.

“Finding a system so close implies that they are common throughout the galaxy.”

Not to nitpick, but how does finding a system nearby indicate it’s commonality in other areas of the galaxy? What if this area of the galaxy just happens to have a high concentration of this type of system?

Ethan: Titan has the advantage of being cold (about 90 K), which makes it much easier for it to retain an atmosphere: the molecules zoom around at slower speeds. Move it in to the habitable zone (about 300 K), and the molecules go faster, so more of them exceed the escape velocity, which is not good.

So if the moon does not have a large quantity of volatiles to replenish the disappearing atmosphere, it will end up dry and barren. However, given the planet is a gas giant, we might expect the moons to have formed from ice-rich material beyond the snowline, so rather than being terrestrial-planet analogues they may be compositionally similar to the icy moons of the outer planets in our solar system.

The question then becomes: suppose we take a lunar-mass icy moon and stick it in the habitable zone, how long could it last before it runs out of water? From this paper the situation looks fairly promising (though the diagram shown only goes down to 0.04 Earth masses) provided the system is younger than 10 billion years, which seems likely. So you might get a lunar-mass “ocean moon” with an atmosphere continually being lost but replenished by the vast quantities of ice in the icy moon’s mantle.

On the other hand, the environment near a gas giant is not a very pleasant place due to radiation belts, etc., and a gas giant in the habitable zone will get a greater flux of charged particles (all the more to sputter your atmosphere away with) than one in the outer reaches of the solar system. Furthermore as you get closer to the star, the region around the planet which is able to support stable orbits for moons gets smaller, which may make it more likely for any moons to be in the really nasty part of the gas giant’s magnetic fields. Unless the moon in question maintains a magnetic field of its own (something that among the moons in our solar system is only found to be the case on Ganymede), this could be problematic.

It would help if the system is at the young end of the range of ages allowed by observations. You might get really pretty aurorae on such a moon from the charged particles in the gas giant’s radiation belts slamming into the upper atmosphere.

Gary, for the solar system that is the subject of this post, it’s all done by measuring the wobble of the host star as it is tugged on by the orbiting planets.

The wobble is minute and only shows up as a tiny change in the light’s frequency (akin to the Doppler effect) as the star wobbles towards and away from us, but it is measurable — just — using today’s technology.

Once you have enough accurate data for the way the star wobbles, you can analyze the results to see how many objects are involved in causing the wobble. If it’s a simple oscillation with a period, say, or five days, then there is likely only one planet (or dim star), but in this case, they found five separate planetary signatures buried in the data — five separate components to the overall wobble of the star. From what I have read, a fifth planet has been suspected for quite a while, but they needed better data before they could confirm it.

As for hunting eclipsing planets, I don’t believe they have found a multiple planet system with that method. Only a small portion of systems will be lined up to allow one planet to pass between us and the host star. I would imagine that the odds of having two or more eclipsing planets in the same system are much smaller (but I’m sure we’ll find some).

I will spare you all my rant about the inability of astronomers ever to come up with a rational nomenclature for anything; suffice it to say for now that a system that decrees that planets are a different kind of thing from stars and then calls the star ‘a’, and the first planet ‘b’, and so on, so that the 5th planet is ‘f’, not ‘e’, is seriously screwed up.

Hmm…given that the first planets found were thought to be extremely eccentric because of the noise in the data, I wonder what this would mean for other known exoplanets who’s orbits are too elliptical to be true?

That’s the line that caught my eye the most of all this. I’ve seen various planet websites showing some of the predicted values for 55 Cancri e for a while now, so this confirmation didn’t surprise me much.

From what I’ve seen, there’s another candidate five planet system already being cross checked.

If super multi planet-bearing stars come in pairs… we found the other one in the “neighbourhood”?

Ah, but I haven’t proposed a mechanism for planet formation that requires pairs of stars dozens of light years apart!

Or… we happen to be in a small neighbourhood of stars with the conditions for multi-planet-ness?

Again, no mechanism. Also, no particular consistency with three figures of known extra-solar planets – presumably. To make more planets in one system, probably you just do the same that you did for the first couple, more carefully.

I’m attracted to the idea that usually the gas giants sweep in from outer orbits into the habitable zone and eat the little fellas, which makes us odd one out (the habitable zone gas giants are the detectable planet systems, ours is not detectable at the necessary distance by wobbling the star), and also for that matter that your own Lagrangian co-mass outgrows its stable locus and more likely hits its big brother planet than going anywhere else (now talking about not gas gaints, necessarily, but where the Moon apparently came from… smacked out of the face of the Earth by a titanic collision), but of course these ideas have to be tested.

I have a question (and I’m sorry if it is such a simple answer, but I am still very new to astronomy though I find it interesting!): How does a gas giant form that close to the star? I thought gas planets had to be further away from the star so that it was cold enough for hydrogen and helium to exist in that state. And if 55 Cancri is much like our sun, wouldn’t these planets need to be just as far away as at least Jupiter?

Again, I am sorry if this is very basic. Ok, back to my History reading…

So, if we were in the 55 Cancri system using this same method to observe our Sun, would we see 4 planets?

Also, while it would seem possible for life to to evolve on a moon orbiting a giant in the habitable zone I’m wondering how stable that life would be to have the time to evolve into intelligent beings. In our case, Jupiter appears to protect Earth from being bombarded with asteriods, limiting the number of extinction events we have endured. However, take a look at Jupiter’s moons and they don’t seem to have fared as well as we have.

“We’ve found you. We know where you are and we’re coming to kill you”
“We’ve found you. We know where you are and we’re coming to kill you”
“We’ve found you. We know where you are and we’re coming to kill you”
…repeat for a few months (w/lots of scary imagery and explosions).

If there is sufficiently-advanced life there and they’ve worked out interstellar travel, nothing will guarantee they’ll come visit us faster than my message. Should be exciting!

What if this area of the galaxy just happens to have a high concentration of this type of system?

Stars don’t stay in the same area; almost all the stars that are near us now were not near us when they (or when our sun, if it is younger) formed. They’re more like cars that happen to be near our car at some point in time when we’re driving on the expressway.

I have a question (and Iâ€™m sorry if it is such a simple answer, but I am still very new to astronomy though I find it interesting!): How does a gas giant form that close to the star? I thought gas planets had to be further away from the star so that it was cold enough for hydrogen and helium to exist in that state. And if 55 Cancri is much like our sun, wouldnâ€™t these planets need to be just as far away as at least Jupiter?

Again, I am sorry if this is very basic. Ok, back to my History readingâ€¦

No need to apologize, we’re all still learning in one way or another

The short answer is that nobody really knows. The current theory is that these “Hot Jupiters” as they have been dubbed (now there’s a good name for a band!) did indeed form much further out from the their host star (i.e. where ours are today).

In the early days of a star system, when a gas giant is formed, there would likely still be a fairly dense disk of gas and dust around the star, and it is thought that as the gas giant plowed through the remaining disk, the resulting friction may have caused its orbit to decay until it was in close orbit around the star.

Of course, that leaves astronomers trying to work out why that did not happen in our own solar system, and whether Earth-like planets could have survived in a system with a hot jupiter.

Here is a fairly recent news story about the work being done in this area:

I will spare you all my rant about the inability of astronomers ever to come up with a rational nomenclature for anything; suffice it to say for now that a system that decrees that planets are a different kind of thing from stars and then calls the star â€˜aâ€™, and the first planet â€˜bâ€™, and so on, so that the 5th planet is â€˜fâ€™, not â€˜eâ€™, is seriously screwed up.

Well, in this case, it’s not as though the initial ordering of designations of extrasolar planets in a system is going to be very useful as we continue to discover smaller and smaller planets. In the end, most multi-planet systems will have a pretty random ordering, depending on which of them was discovered first. So the fact that the first in the sequence is (b) and not (a) when, from innermost to outermost you go something like (b, g, e, f, c, d)!

It is great that a 5th planet has been found there, and in the habitable zone as well. Only problem with the habitable zone is that it does not take the effects of planetary atmospheres into account. In our own solar system the Earth actually lies outside the habitable zone and only Venus lies inside it. And an atmosphere is required for life as we know it to exist. This does not rule out the usefullness of the habitable zone though, since a habitable planet with atmosphere just has to lie a little outside it (or in the outer parts).

But it is interesting that if we only searched for planets inside the habitable zone in our solar system in a search for places where life could be. We would only find Venus there

linusrp: strange how many people come up with this “Earth is not in the habitable zone” argument. For a start, it assumes there is only one way to define the “habitable zone”.

If you define the habitable zone by asking where does a spherical blackbody in equilibrium with solar radiation has a temperature between 0 and 100 degrees C, then sure, you put Venus inside the HZ and Earth outside, but that’s not a very good definition of the HZ (for a start, the habitability of Earth shows you are clearly using an incorrect definition, but I suppose it’s a good one to use if you want to get headlines about how the planet you just discovered around Gliese 581 is habitable).

There are ways of defining the HZ which take greenhouse effects into account, and these do end up with a habitable Earth, but can push the outer boundary to somewhere near Mars. Turns out 55 Cancri f lies at pretty much the exact distance to get the same amount of radiation from 55 Cancri that Earth does from the Sun. So I guess that puts it outside the “habitable zone” as defined in the far-too-simplistic way, but inside the habitable zone when greenhouse effects are taken into account.

The BA said:
“However, gas giants tend to have big moons, and in our solar system they can be as big as Mercury!”

Yes. Or, in the case of Ganymede and Titan, slightly bigger in terms of diameter (because Mercury is so dense, Ganymede and Titan both possess significantly lesser mass than Mercury despite having larger diameters). Callisto is almost exactly the same diameter as Mercury (according to the Nine Planets data, Callisto’s diameter is 39 km smaller than Mercury’s) but its mass is not even one-third as much.

Of course, if you were talking about mass in the first place, Mercury has a much larger mass than either Ganymede or Titan (Ganymede, the largest moon in the solar system, has a mass just a bit less than half of Mercury’s).

>> I donâ€™t see how â€œfinding a system so close implies that they are common throughout the galaxy.â€ Please enlighten me.

Argh, this is the third time this has been asked.

From earlier…

Letâ€™s say you have a blind man sitting in a chair bolted to the floor in a sub-sub-sub basement (maybe itâ€™s a parking garage, itâ€™s huge). His legs are tied to the chair, and elsewhere in the basement there are a random number of dummies in chairs, randomly placed. At the feet of the blind man, within reach (though he has to stretch) are lengths of PVC pipe that can be screwed together to make a pole of increasing length.

The blind man can only detect the dummies first by waving his arms, then by waving a pole. Now for a basement of finite volume, with a random number of dummies being placed randomly, it can be assumed that the average dummy density of the basement is constant (as no other data is known to refine the resolution of the assumption). Therefore, should the blind man be able to touch a dummy with his hands, he could reasonably establish as a working hypothesis, knowing only that there are a random number of dummies randomly placed, that dummies must be common for one to just happen to be right next to him. How the blind man tests this theory is by building a pole and seeing how many other dummies he can thwack with poles of varying lengths, remembering their positions and then getting a more representative sample size.

a system that decrees that planets are a different kind of thing from stars and then calls the star â€˜aâ€™, and the first planet â€˜bâ€™, and so on, so that the 5th planet is â€˜fâ€™, not â€˜eâ€™, is seriously screwed up.

Hmm. But isn’t that system technically making exoplanets objects that are (mostly) “possible planets”? Didn’t the new planet definition (quite reasonably, I think) include gravitationally bound masses that have cleared its orbit?

If so it would exclude immature systems and ejected bodies as well as (I assume) making it difficult to ascertain planet-hood in other systems. I assume planets will have to be declared (and then named) separately.

a system that decrees that planets are a different kind of thing from stars and then calls the star â€˜aâ€™, and the first planet â€˜bâ€™, and so on, so that the 5th planet is â€˜fâ€™, not â€˜eâ€™, is seriously screwed up.

I hate to be nitpicky about formal language, especially with someone who is so excited that even someone like me not into guys have to say it’s cute and obviously more well read then I, but:

> No other star is known to have this many planets.

is of course not at all true – we have a perfectly good example of an eight planet (9-11+ for those who like to call other objects around here planets) system mostly visible from here. Fair short hand given the excitement, but none the less one of those situations where trick questions shouldn’t be tricky to the population at large.

The fact that we have a multiple planet solar system nearby tells me multiple planet systems are very common. These new earth and space based telescopes are going to find many earthlike planets and moons of jovian type planets. All the types of stars have a habitable zone and when we find planets in these zones they must be analyzed.

So why don’t we blast a super-powerful signal to that general area to see if there is any response? I don’t see the harm in such an experiment. Send out a signal, and wait for an answer. I might not be around in another 82 years, but my kids might, and hopefully so will a scientific community. Its worth a shot. Tell me if I’m wrong in some way, please!

I believe in God. I believe in creation. I also have an open mind to new things. I think that it is naive to think that we are the only people in the entire universe. Well maybe not “people” but you get it, right? I feel that God made a world, it wasn’t perfect so he went far enough away to where we would never find the next one, and made a new world, it wasn’t perfect, and so on. Forever on a search for the perfect world in a never ending cycle. Until one day, he will make it, then he will go to the start of his line and come back and take all of the believers with him. Then go on to the next planet and take all the believers. (The Rapture)

My theory. You can take it or leave it, it doesn’t bother me any. Just letting you know my view on things.

wow thrilled and not thrilled rofl. never in astronomy history am i so DISSAPOINTED (along with pluto is not a planet) at attention seeking people. Now i am a science lover and astronomy buff dont get me wrong, but if i told you that ive detected elvis was alive with blurry photographic evidence, youd be sitting here all laughing at me right about now.
proof, proof, proof! i am tired of overboastfull claims of finding planets
based on star wobbling, show me full, clear color photos!
whatever happened to the scientific method?
if i told you there is an ant farting on mars right now based on how mars shimmers, you would all be laughing.
these are like listening to peoples antedotes about ghosts, only with no photographic evidence other than half baked theories. Not that the theories arent wrong but its much like even stephen hawking getting in the fray theorizing about black holes wich not only we cant see, probably wont be able to see. Now if i were to write books or papers on matters
without giving clear cut proof of scientific order, id generaly be laughed at but am wondering why are we taking these people so seriously and
isnt it a bit dangerous as well as mind numbingly boring.
lets put it this way, yes i believe planets are out there, but astronomy
is a visual art form and me remarking about planets we cant see and
making discoveries that are speculation is a little like me takling
about the lost picasso paintings my grandpa thinks might be in his
attack over in yakima. a waste of time and much like canals on mars,
better be sure of what your saying with visual PROOF.
and creationalists and religionists are scared of astronomy because
it will likely prove the universe far older and may be able to finaly
show religions are man made nonsense. but hey millions of people
believe in things they cant see like elvis still being alive and god.
sad to see weve added bad science and bad astronomy to the lot.